Instrumentation is used widely for accessing blood and other target physiological tissues, structures or organs and gathering information therefrom for medical and scientific purposes. Instrument components of these instrumentation include miniature electronic and electromechanical devices or microsystems, which may be implanted or otherwise disposed within the body of a patient or biological specimen in proximity to the target tissue, structure, or organ for direct (or close) contact therewith. As they perform their operations, such devices consume energy.
Finite power supplies for these devices, such as batteries, must be replaced or recharged upon inevitable exhaustion of their available energy, which with implants entails at least some level of unwanted invasiveness. Batteries also add undesirable size and weight to the device, and depending upon their chemical composition and packaging, may introduce medical or biological risk with implant use. Powering the implanted devices through leads, conduits, or the like from an external power source however entails undesirable penetration of the patient or specimen and varying levels of associated discomfort, inconvenience and possibly a risk of infection.
More recently, implanted medical and physiological (hereinafter “medical”) instrumentation components have included wireless microsystems. Such wireless microsystems are powered and exchange data signals or otherwise communicate with “outside world” instrument components, disposed external to the patient or specimen, outside of the body of the patient or specimen (hereinafter “patient”) in which the implanted microsystem device is disposed.
For example, power may be supplied to an implanted wireless microsystem from an external power source by electrical induction using magnetically coupled transformer coils. An external coil is brought into proximity and alignment with a coil implanted within the body of the patient. Power may be supplied to the implanted wireless microsystem upon attaining a critical coupling, in which the coil of the external source supplies power inductively to the implant coil.
While the implant may be thus powered, the inductive coupling may be operable at frequencies too low to support efficient intercommunication at modern data rates. Further, the implanted coil occupies space and weight in vivo, which may entail unwanted invasiveness and discomfort.
“Radio communications” may also be used in which power supply and data exchange interactions with the implanted microsystem are made at microwave frequencies from an external radio frequency (RF) source. The signal exchange transactions with the microsystem and its power supply entail coupling via an antenna sub-component implanted therewith.
The implanted antenna, however, also occupies space and weight in vivo and may further entail some degree of undesirable microwave bioexposure during its operation. Optical communications may mediate or ameliorate some of these instrumentation related issues discussed above.
Optical communication using lasers or light-emitting diodes (LEDs) may allow signal interchange with implanted medical instruments as well as power supply thereto. For example, a laser or LED light source and associated photodetector external to the body of the patient may transact or otherwise exchange data signals with a phototransceiver component of an implanted microsystem and/or provide power to a photovoltaic-driven power generation component thereof.
However, significant issues remain to be overcome relating to optical scattering and absorption and other optical characteristics of biological tissue, structures, organs, and fluid filled vessels in or near where the instrument may be implanted and/or between the instrument and the light source for some practical implementations of powering implanted medical or physiological instruments or exchanging data signals therewith optically.
Power and signal transfer through human skin may be subject to significant loss by optical scattering in epithelial tissue and optical absorption by melanin and other pigments and substances. Transcutaneous optical communication and power transfer systems demand additional power to cover such losses.
Moreover, the thickness of tissue between capillaries at which detector components may be disposed at the skin surface typically exceeds one millimeter. At this thickness, however, handling the optical transceiver (power supply and reader) component in place for proper alignment to preserve sufficient optical coupling becomes challenging.
For example, optical power levels demanded from an incident laser or LED source for driving sufficient on-chip operating currents and voltages on the implanted instrument component may exceed tissue damage thresholds. Pulsed optical drivers for overcoming this power transfer issue add complexity and expense, while possibly partially reducing reliability.
Approaches described in this section may or may not have been conceived or pursued previously. Unless otherwise indicated, it should not be assumed that any approaches discussed above include any alleged prior art merely by any such discussion. Not dissimilarly, any issues discussed in relation to any of these approaches should not be assumed to have been recognized in any alleged prior art merely based on any such discussion above.